The efficiency of a customized distalizer with Variety SP® screws anchored on palatal miniscrews for upper molar distalization

ABSTRACT Objective: To assess the effectiveness of a customized distalizer with Variety SP® screws anchored on palatal miniscrews for upper molar distalization. Methods: Seventeen patients aged between 12.5 and 24 years underwent distalization with a customized distalizer. Lateral cephalogram and cast analysis were performed before and after distalization. Linear and angular parameters of the upper first molar, first premolar, and central incisor were assessed. Results: Distalization with the force passing near the center of resistance (CRes) of the upper first molars resulted in distal movement, with minimal distal tipping (2.8 ± 0.45°, p< 0.05). However, distalization passing occlusal to the CRes led to greater distal tipping (13.6 ± 1.63°, p< 0.05). Statistically significant spontaneous distal tipping and distal movement of the upper first premolars occurred, with a mean of 6.2 ± 1.24° (p< 0.05) and 0.68 ± 0.34 mm (p< 0.05), respectively. The positional change of the upper central incisors presented a mean of -0.23 ± 0.1 mm (p> 0.05) and 2.65 ± 1.1° (p< 0.05). Upper first molar intrusion was statistically significant, with a mean of 0.88 ± 0.2 mm (p< 0.05). Upper right and left first molars rotation towards palatal midline presented mean of 4.1 ± 0.19° (p< 0.05) and 3.4  ± 0.1° (p< 0.05), respectively. Additionally, the distance between upper right and left first molars increased significantly, with a mean of 2.54 ± 0.01 mm (p< 0.05). Conclusion: The study successfully demonstrated the efficiency of molar distalization without anchorage loss using a customized distalizer anchored on palatal miniscrews.


INTRODUCTION
Distalization of upper molars as a method for correction of upper crowding is getting more and more popular as an alternative to premolar extraction.Despite the large number of molar distalizing devices, orthodontists prefer compliance-free intraoral bonded appliances.There are many types of intraoral distalizers known by orthodontists, for example: Distal Jet, Pendulum, Jones Jig, iPanda, etc.Many of them have disadvantages, such as loss of anchorage, molar tipping and rotation during distalization and compromised oral hygiene.The Pendulum appliance, introduced by Dr. James Hilgers in 1992, is one of the most popular options.
Various modifications of the Pendulum appliance exist today.
Byloff et al. 1 conducted a study to evaluate the dental and skeletal effects of the Pendulum appliance.The results demonstrated that the pendulum appliance moved molars distally without creating a dental or skeletal bite opening, with little anchorage loss.However, a significant amount of molar tipping should be considered when using this appliance.In the study of Bussick et al. 2 , the mean distalization with the Pendulum appliance was 5.7 mm.
Intraoral distalization appliances typically comprise a distalizing mechanism and anchor teeth.To prevent anchorage loss during distalization, orthodontists have started using distalization appliances in combination with palatal miniscrews.A study by Kinzinger et al. 3 evaluated the effectiveness of a skeletonized distal jet appliance for maxillary molar distalization.In the area of the cement-enamel junction, the permanent first molars were distalized by a mean of 3.92 ± 0.53 mm and intruded by a mean of 0.16 ± 0.26 mm.At the same time, they experienced distal tipping of 2.79 ± 2.51°.The first premolars, included in the anchorage setup, mesialized by 0.72 ± 0.78 mm and simultaneously tipped by 1.15 ± 2.98° to the palatal plane.They also reported an increase in transverse widths and mesiopalatal rotation of both right and left upper first molars. 3ec et al. 4 , in their meta-analysis, compared the effects of intraoral distalizers with conventional and skeletal anchorage.
They concluded that molar distalization was effective with both anchorage systems.The amount of distal molar movement was 3.34 mm with conventional anchorage and 5.10 mm with the skeletal anchorage system.The conventional anchorage system showed anchorage loss, represented by a premolar mesial movement of 4.01 mm 4 .
It is known that some intraoral palatal distalizers induce the rotation of upper first molars around the palatal root during distalization, due to a force passing palatally to the center of rotation of the molar 5 .Kinzinger et al. 6 evaluated the biomechanics of a distal jet appliance, and reported that during the application of force palatal to the center of resistance (CR es ) of the upper first molars, the teeth experienced therapeutically undesired mesial-inward and distal-outward rotation.To mitigate rotational movement and extend overall treatment duration, the approach of the present study utilizes a rigid and resistant distalizing mechanism, capable of counteracting molar rotation and intrusion, while also providing reliable anchorage post-distalization.Thus, the objective of this study was to assess the type of distal movement observed in upper teeth when utilizing a palatal distalizer with Variety SP ® screws anchored on palatal miniscrews.Preoperative mouth-rinsing with a 0.1% chlorhexidine solution was performed two days before and on the day of insertion.

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Local terminal anesthesia, using an adrenaline-free anesthetic, preceded the placement of the two miniscrews with neck and collar lengths of 8 mm and a diameter of 1.65 mm (Tomas, Dentaurum, Germany).The miniscrews were positioned in the paramedian region of the maxilla in the anterior palate area, using a manual screwdriver without predrilling.
Primary stability tests were conducted for all miniscrews.Three patients, experiencing palatal soft tissue inflammation after the initiation of distalization and requiring appliance removal, were excluded from the study.In four cases, upper third molars were extracted before the initiation of distalization.However, in the remaining thirteen cases, the upper third molars were in the germinating stage, eliminating the need for extraction.
Immediately after miniscrew insertion, impressions for the distalizing appliance confection were taken, using Zhermack Elite HD+ A-Silicone material.These impressions were promptly sent to a technician for the fabrication of the appliance.
It is commonly believed that titanium alloy miniscrews may undergo partial osseointegration approximately three weeks after insertion. 7,8Hence, our decision was to bond the appliance after this three-week period.Patients were instructed to activate the distalizing screws on each side with a quarter turn per week.In three cases, patients faced difficulties during self-activation, leading the orthodontist to perform the activations.
Lateral cephalograms were captured using Planmeca Promax 3D (Helsinki, Finland) before (T1) and after (T2) distalization for all ten patients.All lateral cephalograms were analyzed using Dolphin Imaging software by the same operator, who performed the analysis twice at a 2-week interval.In cases in which differences in measurements arose, the means of both readings were utilized in the subsequent statistical analysis (Figs 3 and 4).A decrease in the angle between the line passing through the mesiobuccal cusp tip and mesiopalatal cusp tip and the palatal midline was indicative of first molar mesial-inward rotation.For intermolar width evaluation, the distance between the mesiobuccal cusp tips of the left (UL6) and right (UR6) first molars was measured, and an increase in this measurement indicated expansion.
The calculated parameters are detailed in Table 1.

STATISTICAL ANALYSIS
To assess the reliability of cephalometric measurements and cast analysis, two sets of measurements were taken for each participant, at two-week intervals.The possible error between the two sets of measurements was calculated using the Dahlberg formula.Differences with a significance level p < 0.05 (5%) were considered statistically significant.The relationship between distal tipping of upper molars and distal movement, as well as distal tipping and intrusion, was assessed using the Pearson correlation coefficient (r).
The primary objective was to reject the null hypothesis, thereby affirming the effective distalization of the upper first molars induced by the appliance.

RESULTS
The mean distalization duration was 6.8 months.The possible error between the two sets of cephalometric measurements calculated using the Dahlberg formula, yielded a value of 1.1° for angular measurements and 0.8mm for linear measurements.For cast analysis, Dahlberg formula revealed possible error of 2.3° for angular and 0.6 mm for linear measurements.
Dental Press J Orthod.2024;29(2):e2423253 The results of T1 and T2 cephalogram analysis are shown in      The upper first premolars tipped distally (U4/SN) on average In the present study, we investigated the relationship between upper first molar distal tipping and distal movement.
The Pearson correlation coefficient (r = -0.0052)suggests a very week linear relationship between upper first molar distal tipping and distal movement.This suggests that the degree of distal tipping was not significantly associated with the amount of distal movement in the present study sample.
Distal tipping of the upper first molar is more pronounced when the second molar is in the germinating phase. 10In the present study, ten cases involved fully erupted second molars, while In our study, when the force passed near the CR es of the first molar, we observed vertical movement that was statistically insignificant.However, in five cases, when the force passed occlusal to the CR es , we observed significant intrusion along with distal tipping.The occurrence of intrusion during distal tipping of the molar suggests a complex biomechanical interplay.
To gain a deeper understanding of this phenomenon, further investigation through finite element analysis is recomended.
In a systematic review, Fiorillo et al. 15 assessed eleven studies and concluded that upper molars can be effectively distalized with Temporary Anchorage Device (TAD)-assisted distalizing appliances, achieving a range of 3.0 to 5.3 mm.Spontaneous distal migration of upper premolars was observed, ranging from 1.65 to 4.30 mm.In our study, distal migration was 0.57mm, but the distal tipping was 5.13°.The only plausible explanation for distal tipping with minor migration is the growth-induced changes observed in the majority of patients included in this study. 16The distal tipping of upper premolars can be attributed to the use of a direct skeletal anchorage system in our study, where premolars were not included in the anchorage unit.
They tipped distally due to the stretching of transseptal fibers. 17To prevent anchorage loss, the appliance in this study was supported by two palatal miniscrews.Grec et al. 4 concluded in their study that intraoral distalizers with skeletal anchorage, unlike traditional systems, were more effective for molar distalization and showed no anchorage loss.Moreover, the use of direct skeletal anchorage induced spontaneous distal movement of upper premolars.Ludwig et al. 18 suggested that the anterior palate is a reliable zone for miniscrew insertion.In our study, miniscrews were consistently placed 3-4 mm parasagittal to the midpalatal suture in all patients.
In nine cases, the distance U1 CEJ./PTV was increased; and in six cases, U1/SN angle was increased.Given the use of direct skeletal anchorage, the only plausible explanation for the increase in results could be the growth-induced changes and possible errors during measurements. 16other possible reason could be the fact that in several cases brackets were bonded to upper teeth before the completion of distalization.
Another important factor that needs consideration during distalization is the stiffness of the distalizing appliance.

Poghosyan D , 5 Dental
Grigoryan D, Ter-Poghosyan D, Gunaveerasekaran G, Dara S, Ter-Poghosyan H -The efficiency of a customized distalizer with Variety SP ® screws anchored on palatal miniscrews for upper molar distalization patients, comprising three boys and fourteen girls aged between 12.5 and 24 years, were randomly chosen for bilateral upper molar distalization.The purpose of this intervention was to address dentoalveolar Class II malocclusion and dental arch length discrepancies.The inclusion criteria encompassed patients with edge-to-edge Class II molar relationships and mild to moderate crowding in the maxilla.Exclusion criteria involved individuals with skeletal constriction of the maxilla, those who had undergone unilateral molar distalization, individuals with a history of prior orthodontic treatment, and those with insufficient oral hygiene.Poghosyan D, Grigoryan D, Ter-Poghosyan D, Gunaveerasekaran G, Dara S, Ter-Poghosyan H -The efficiency of a customized distalizer with Variety SP ® screws anchored on palatal miniscrews for upper molar distalization Dental Press J Orthod.2024;29(2):e2423253 All patients and their parents were provided with detailed information regarding the necessity of distalization and the associated procedures.Consent was obtained through the signing of an agreement form.The distalizing appliance comprised a palatal acrylic Nance button securely bonded to two palatal miniscrews.Utilizing two 12.0-mm long Variety SP ® expansion screws (Dentaurum GmbH & Co. KG, Turnstr.31, 75228 Ispringen, Germany), positioned parallel to the alveolar crest and extending from the acrylic Nance button, the screws were welded to the upper first molar bands.The connecting wire had a diameter of 1.48 mm (Figs1 and 2).

Figure 6 :
Figure 6: An example of cast analysis.
U4 = Upper first premolar, PTV = pterygoid vertical, U6 = Upper first molar, U1 = Upper incisor, CEJ = Cementenamel junction, SN = Sella-Nasion line, mes.cusp = mesiobuccal cusp tip, FH = Frankfort Horizontal.U4-dis.point /PTV: the distance between the most distal point of the maxillary first premolar to the pterygoid vertical U6-dis.point /PTV: the distance between the most distal point of the maxillary first molar to the pterygoid vertical U1 CEJ./PTV: the distance between the cement-enamel junction of the maxillary central incisor to the pterygoid vertical U1/SN: the angle between the axis of the maxillary central incisor and the anterior cranial base U4/SN: the angle between the axis of the maxillary first premolar and the anterior cranial base U6/SN: the angle between the axis of the maxillary first molar and the anterior cranial base U6 mesial cusp/FH: The distance between mesial tip of the maxillary first molar and Frankfort horizontal

6. 2 ± 1 .
24° (p < 0.05), and the mean change in distance between U4-dis.point and PTV was 0.68 ± 0.34 mm (p < 0.05).The distance from the cement-enamel junction of the maxillary central incisor to the PTV point (U1 CEJ./PTV) was increased in some patients and decreased in others, but the mean change was -0.23 ± 0.1 mm (p > 0.05).On the other hand, the maxillary central incisors were tipped palatally 2.65 ± 1.1° (p < 0.05).The mean change in distance between the mesiobuccal cusp tip of the maxillary first molar and the FH was 0.88 ± 0.2 mm (p < 0.05).In twelve cases, the distance remained unchanged or exhibited statistically insignificant differences, with a mean 0.29 ± 0.04 mm (p > 0.05).However, in five cases, intrusion of the upper first molars was observed, with a mean of 2.3 ± 0.79 mm (p < 0.05).The Pearson correlation coefficient (r) between upper first molar distal tipping and intrusion was 0.47.Additionally, the Pearson correlation coefficient (r) between upper first molar distalization and distal tipping was -0.0052.Distance between mesiobuccal cusp tips of upper right and left first molar increased a mean of 2.54 mm (p < 0.05).The angle between mesiobuccal cusp-mesiopalatal cusp tips and palatal midline decreased a mean of 4.1 ± 0.19° (p < 0.05) and 3.4 ± 0.1° (p < 0.05) for UR6 and UL6 respectively.Dental Press J Orthod.2024;29(2):e2423253DISCUSSIONIn twelve cases, the upper first molars moved distally almost bodily, with minor distal tipping.However, in five cases, the molars tipped distally significantly, in conjunction with distal movement.The biomechanical explanation could be the force passing occlusal to the CR es of the upper molars.According to Gandhi et al.9 , the CR es of the maxillary first molar is situated apically and distally to the trifurcation area.Its specific location can vary among different patients.To ensure controllable movement, it is crucial to consider the tooth CR es during the process of distalization.However in some cases, due to insufficient palatal depth, technicians find it challenging to place distalizing screws deep enough for the force to pass near the CR es of the first molars.

Poghosyan D ,
Grigoryan D, Ter-Poghosyan D, Gunaveerasekaran G, Dara S, Ter-Poghosyan H -The efficiency of a customized distalizer with Variety SP ® screws anchored on palatal miniscrews for upper molar distalization 18 Dental Press J Orthod.2024;29(2):e2423253 in seven cases, the second molars were in the eruption phase.In these seven cases, we observed distal movement with small distal tipping of the upper first molars.Kircali et al. 11 evaluated the dentoalveolar and dentofacial effects of a miniscrew-supported pendulum appliance during upper molar distalization, reporting 4.2 mm of first molar distalization, significant distal tipping of 8.9°, and a significant intrusion of 0.6 mm.In another study, Cozzani et al. 12 reported 4.7 ± 1.6 mm of distalization, 2.8° of distal tipping, and 0.7 mm of intrusion in the upper first molars using a group of miniscrew-supported distal jet appliances.Chiu et al. 13 , in their comparison of two intraoral molar distalization appliances (distal jet versus pendulum), reported 1.7 ± 1.4 mm of extrusion of the U6 in the distal jet group and 1.6 ± 1.2 mm in the pendulum group.In another study, Tekale et al. 14 reported 0.25 mm of intrusion movement on the distal cusp of the maxillary first molar and 0.14 mm of extrusion movement on the mesial cusp of the first molar in the Z direction.Kinzinger et al. 3 reported a mean extrusion of the first molar of 0.63 ± 0.70 mm.In another study, Kinzinger et al. 6 evaluated the biomechanics of a distal jet appliance, indicating that a -21 cN intrusive force acted on the upper first molar during distalization.This force remained stable until 1-mm of distal movement, after which it consistently dropped.Dental Press J Orthod.2024;29(2):e2423253

Poghosyan D , »»»»Dental»
photographs.»The authors report no commercial, proprietary or financial interest in the products or companies described in this article.

Table 1 :
Lateral cephalogram landmarks and measurements used in this study.

Table 2 .
Mean and standard deviations of T1 and T2 analysis are shown in Table3.

Table 2 :
The results of T1 and T2 cephalogram analysis.

Table 3 :
T1 and T2 cephalogram and cast data statistical analysis.

Ter-Poghosyan D, Gunaveerasekaran G, Dara S, Ter-Poghosyan H -The efficiency of a customized distalizer with Variety SP ® screws anchored on palatal miniscrews for upper molar distalization 22 Dental
21rce distalizer (DFD) was 5 months.21Inour study, the mean distalization time was 6.8 months.Poghosyan D, Grigoryan D, Press J Orthod.2024;29(2):e2423253 22nzinger et al.3reported mean increase in transverse width of Kircali et al.22reported an increase in the distance between mesiobuccal cusps of the upper first molars by 2.4 mm, along with insignificant mesiopalatal rotations of the upper first molars.